Mechanically latched mercury switches



United States Patent Ofiice 3,198,9l l Patented Aug. 3, 1965 3,198,911 ME CHARHCALLY LATCHED MERQURY SWITQHES l'rving l2. Mitchell, Roclrviile Centre, N."i(., assignor to Ebert Electronics (Zorn, Queens Village, N.Y., a corporation of. New Yuri:

Filed Mar. 29, 1963, Ser. No. 263,175 '7 Claims. (Cl. Mill-dill) The present invention relates generally to mercury switches, and more particularly to mechanically latched mercury switches of the plunger type.

A common plunger type mercury switch employs a magnetic plunger, which in one of its positions is immersed in a pool of mercury and therefore raises its level sufficiently to complete a circuit, and in its other position removed from the pool, to lower the level of the pool sufiiciently to break the circuit. Bias force applied to the plunger, as by a weight or spring, may retain the plunger normally depressed against its own buoyancy, and magnetic force may be employed to overcome the bias, in one type of switch, or the plunger may normally float and be depressed by the magnetic force, in another. In either case continued application of magnetic force is required to maintain the plunger in actuated position, in prior art switches, so that continued energizing current in an actuating coil is required.

It is desirable to provide a mercury plunger type relay which may be actuated into either of its operative conditions, i.e. circuit open or circuit closed, in response to a short pulse of operating current, and which automatically and mechanically latches itself in either condition, when so transiently actuated.

In accordance with one embodiment of the invention, the magnetic plunger of a mercury plunger switch is associated with or secured to two helical springs, each having an outer diameter sligthly greater than the inner diameter of the switch envelope. Two actuating coils are provided, one of which moves the plunger up when energized, and thus breaks the switch circuit, and the other of which moves the plunger down into circuit making position. The helical springs are secured, one to the top of the plunger, and the other to the bottom. When the plunger moves down, the upper spring is tensed and hence reduces its outer diameter. The lower spring had been placed in stretched condition and hence is of reduced diameter, before the movement. Accordingly, the plunger can move down into the mercury. Once the movement is complete, the lower spring increases its diameter, since it is compressed, and locks against the inner wall of the switch envelope, holding the plunger in depressed position. In similar manner, when the upper coil is energized the tension in the lower spring is overcome and permits movement of the plunger into its upper position, where it is retained after the movement is completed, by the compressed upper spring binding against the inner wall of the switch envelope.

The two springs thus act in alternation to retain the plunger in either actuated position.

In accordance with a modification of the invention, one or more hook springs are provided internally of a mercury plunger envelope. In accordance with one modification of the invention, the springs are secured to the plunge and move therewith. One or more stationary protuberances are provided internally of the envelope, which are so located that the hook spring, in either of the final or actuated positions of the plunger, latches the plunger in that position. In the alternative, the hook spring may be secured to the envelope and the protuberance provid d on the plunge As a further modification or" the invention, a single helical spring may surround the plunger being retained with respect thereto in any convenient way, and may act as a frictional latch.

It is, accordingly, a broad object of the invention to provide a novel mercury plunger switch having a device for latching the plunger in either of two actuated positions within its envelope.

It is another object of the invention to provide a device consisting of one or more helical springs, secured to the plunger of a mercury plunger relay, and which have an outer diameter slightly greater than the inner diameter of the switch envelope, whereby the spring or springs bind within the envelope and latch the plunger, but can be moved against the tension of the spring or springs when the plunger is actuated.

A further object or the invention resides in a novel latching device for an object moving within a tube, consisting of a binding helical spring.

Still another object of the invention resides in the provision of a resilient hook device for detachably latching the plunger of a mercury plunger switch, in either of its actuated positions.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a view in longitudinal section of a first embodiment of the invention;

FIGURES 2-4 are views in longitudinal section, of various modifications of the switch of FIGURE 1; and

FIGURE 5 is a circuit diagram of the switches of FIG- URES 13, inclusive.

Referring now more specifically to the accompanying drawings, the reference numeral 10 denotes an envelope or container for a mercury plunger switch which may be fabricated of plastic or vitreous material, or of metal with suitable provision for insulating various electrodes. Mercury plunger switches are well known which utilize envelopes of these various types.

Assuming, for the sake of example only, that the envelope or container 10 is provided with a metallic outer shell, H, the latter may be internally insulated by a plastic liner 12, nylon or nylon impregnated with glass fiber being suitable insulating material. Within the liner 12 is located a pool 13 of mercury, into which extends an electrode 14. The latter extend insulatedly through the bottom of the envelope it and terminates in a lead 15. The lead 15 is in permanent connection with the mercury pool 15.

A further electrode to is provided, which is located within a cup 17 of insulating material, extending upwardly through its bottom, and being connected by an insulated lead 18 to a point externally of envelope It).

A magnetic plunger 20 is provided which floats in the pool 13. Such plungers are normally constructed as ceramic cylinders surrounded with a sleeve of magnetic material.

The quantity of mercury in the pool 13 is so selected that when the plunger 2%) is raised the level of the pool 13 is below the rim of the cup 17. No circuit then exists between leads l5 and 18. When the plunger 20 is depressed the level of the mercury pool 13 is raised and overflows the cup 17, thus completing the circuit between leads i5 and 18.

Included within the liner 12 are two helical springs 22 and 23, of which spring 22 is secured to the upper end of plunger 29*, and spring 23 is secured to the lower end. The springs 22. and 23 have outer diameters slightly greater than the inner diameter of liner 12. In the quiescent condition of the plunger then, whether raised or depressed, the springs 22, 2 3 retain the plunger 2% in position. However, the resilience of the springs is such that when the ,9 plunger is actuated the springs release their grips on the liner 12 and permit motion of the plunger. One of the springs 22, 23 is always in compression and the other always in tension, when the plunger 2t; is in one of its limiting positions, and that alternate conditions obtain for the other position, and hence one of the springs 22, 23 always is in condition, i.e. in compression, to hold or latch the plunger 20.

Two actuating coils 25', 26, are provided externally of envelope 1%, to actuate plunger 2%. Coil 2.5, when energized, raises the plunger 2% and coil 26 lowers or de presses it. Coils 25, 26 are selectively energized by means of off-on switches 27, 28. The mercury contacts are represented by numerals 14, 16 in FIGURE 4 and the corresponding terminals by numerals 15, 18, so that corresponding elements in FIGURES 1 and 4 bear corresponding numerals of reference.

In accordance with a modification of the present invention, illustrated in FIGURE 2, the helical springs 22, 23 are dispensed with, and a pair of hook springs 31 substituted. The sprin s 3t), 31 extend upwardly from and are secured to the plunger 2% at diametrical points thereof, and are provided with bends or hooks 32, 33, which ride on the liner 12. The latter is provided with protuberances 34, 35, which are located vertically at such positions that the bends or books 32, 33 are located over the protuberances when plunger 29 is raised and under same when lowered. The bends or hooks 32, 33 thus releasably maintain the plunger 29 in its last actuated position, whether raised or lowered. The circuit of FIGURE 4 applies to the structure of FIGURE 2.

In the alernative, hook springs 49, 41 may be secured immovably to the liner 12 and the plunger 2%) may be provided with locking protuberances 42, 43, as illustrated in FIGURE 3.

In accordance with still a further modification of the invention, illustrated in FIGURE 4, a single helical spring surrounds the magnetic plunger 26. The spring 50 has a slightly larger outer diameter than the inner diameter of envelope 10. The spring 5t may be held in place, or secured to plunger 20, in any convenient manner. T he spring 50 is designed to provide suificient friction with the envelope wall to hold the plunger 20 in place, except when subjected to force due to actuating coils, as 25, 26.

While I have described and illustrated one specific embodiment of my invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

What I claim is:

1. A mercury plunger latch relay, comprising a container having therein a pool of mercury, a first contact permanently contacting said pool of mercury, a second contact, a magnetic plunger, means normally isolating said second contact from said mercury while said plunger is in one position relative to said pool of mercury, said pool of mercury being raised in response to increased immersion of said plunger in a second position with respect to said pool of mercury to a level adequate to achieve contact with said second contact, activatable magnetic means for selectively etfecting movement of said plunger to said one position and to said second position, and latch means located internally of said container for retaining said plunger in its last position preceding de-activation of said magnetic means, said latch means including at least one spring member fastened to said plunger for frictional engagement with said container at said plunger positions, the frictional force exerted during said engagement being sufiicient to retain said plunger in said last position and being less than the force exerted on said plunger upon activation of said magnetic means.

2. The combination according to claim 1 wherein said container is cylindrical and wherein said latch means is a coil spring means having a normal outer diameter greater than the inner diameter of said container, said spring means being secured to said plunger.

3. The combination according to claim 1 wherein said container is cylindrical and wherein said latch means includes two helical springs, said helical springs being located at alternate ends of said plunger and having ends secured to said plunger, said helical springs having greater outer diameters when in unstressed condition than the inner diameter of said container.

4. The combination according to claim 1 wherein said latch means includes a spring element, a protuberance, said spring element being secured to one of said plunger and container, said protuberance being secured to the other of said plunger and container.

5. The combination according to claim 1 wherein said container is cylindrical and wherein said latch means includes a helical spring having a greater outer diameter than the inner diameter of said container, and means confining said helical spring between the ends of said plunger.

6. A mercury latching relay comprising an envelope; a pool of mercury within said envelope; a pair of electrodes proiecting into said envelope, one of said electrodes being permanently immersed in conductive relation with said pool of mercury; a mercury-displacing magnetic plunger within said envelope; coil means effective when energized to selectively actuate said plunger to respective first and second positions within said pool of mercury to displace the level of said pool; said electrodes being couduct-ively bridged via said pool of mercury when said plunger is in one of said first and second positions, and being insulated from each other when said plunger is in the other of said positions; and latching means including at least one spring member fastened to said plunger for frictional engagement with said envelope to releasably retain said plunger in either of said first and second positions upon actuation thereto, so that said relay may be pulsed to either a closed or an open condition and maintained therein until subsequently pulsed to the other condition.

7. The combination according to claim 6 wherein catch means are provided on the inner wall of said envelope for cooperating with said spring member for said retention of said plunger.

References (Jited by the Examiner UNITED STATES PATENTS 2/03 Ashley. 9/43 Harvey. 

1. A MERCURY PLUNGER LATCH RELAY, COMPRISING A CONTAINER HAVING THEREIN A POOL OF MERCURY, A FIRST CONTACT PERMANENTLY CONTACTING SAID POOL OF MERCURY, A SECOND CONTACT, A MAGNETIC PLUNGER, MEANS NORMALLY ISOLATING SAID SECOND CONTACT FROM SAID MERCURY WHILE SAID PLUNGER IS IN ONE POSITION RELATIVE TO SAID POOL OF MERCURY, SAID POOL OF MERCURY BEING RAISED IN RESPONSE TO INCREASED IMMERSION OF SAID PLUNGER IN A SECOND POSITION WITH RESPECT TO SAID SPOOL OF MERCURY TO A LEVEL ADEQUATE TO ACHIEVE CONTACT WITH SAID SECOND CONTACT, ACTIVATABLE MAGNETIC MEANS FOR SELECTIVELY EFFECTING MOVEMENT OF SAID PLUNGER TO SAID ONE POSITION AND TO SAID SECOND POSITION, AND LATCH MEANS LOCATED INTERNALLY OF SAID CONTAINER FOR RETAINING SAID PLUNGER IN ITS LAST POSITION PRECEDING DE-ACTIVATION OF SAID MAGNETIC MEANS, SAID LATCH MEANS INCLUDING AT LEAST ONE SPRING MEMBER FASTENED TO SAID PLUNGER FOR FRICTIONAL ENGAGEMENT WITH SAID CONTAINER AT SAID PLUNGER POSITIONS, THE FRICTIONAL FORCE EXERTED DURING SAID ENGAGEMENT BEING SUFFICIENT TO RETAIN SAID PLUNGER IN SAID LAST POSITION AND BEING LESS THAN THE FORCE EXERTED ON SAID PLUNGER UPON ACTIVATION OF SAID MAGNETIC MEANS. 